1. Field of the Invention
This invention pertains to connectors for terminating coaxial cables. More particularly, this invention pertains to such a connector which includes means to lock a center pin in place to eliminate relative axial movement of the center pin within the connector.
2. Description of the Prior Art
In the prior art, coaxial cable connectors (such as well-known BNC or TNC connectors) are commonly used to terminate coaxial cables. Coaxial connectors include a metallic housing having a cylindrical sleeve. Centrally disposed within the sleeve is a center contact pin. The center contact pin is maintained in coaxial alignment within the sleeve by means of a dielectric spacer. The geometry of the pin, spacer and sleeve are mutually selected for the BNC connector to have a prescribed characteristic impedance (for example, 75 ohms).
A coaxial cable consists of a center conductor wire surrounded by an inner dielectric sheathing. A flexible, tubular mesh of conductive material (referred to as a ground shield) surrounds the dielectric sheathing. Finally, an outer insulating sheathing would surround the shield.
In the prior art device, the center conductor of the coaxial cable is secured to the center pin of the BNC connector through any suitable means (for example, by crimping or solder). The grounded shield of the coaxial cable is secured to the BNC housing through any suitable means (commonly, by crimping). As a result, the cylindrical sleeve of the BNC connector is electrically grounded and the center pin is electrically connected to the center conductor of the coaxial cable.
From time to time, axial forces can be placed on a coaxial cable. In response to such forces, the center pin of the BNC connector experiences forces urging it to move axially within the sleeve. Such movement is undesirable. However, with the prior art designs of BNC connectors, the center pin would be susceptible to movement resulting from environmental effects (for example, axial forces applied to the cable) and temperature fluctuations (resulting in relative movement of the center pin due to different coefficients of expansion). If relative movement were to occur, it would be possible for the center pin to become disconnected from a second coaxial cable mated to the BNC connector. In this event, signal interruption could occur.
With prior art BNC designs (or alternatively TNC type connectors), relative movement of the center pin within the connector is common when extreme temperature fluctuations occur. However, since coaxial cables handle very fast transmission rates (for example, about 45 megabits per second), even low probability circuit interruptions are extremely undesirable. It is an object of the present invention to provide a coax cable connector which avoids movement of a center conductor pin.